/in/foo.c: In function 'main':
/in/foo.c:8:10: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[50]' [-Wformat=]
  scanf("%s %s",&a,&b);
          ^
/in/foo.c:8:13: warning: format '%s' expects argument of type 'char *', but argument 3 has type 'char (*)[50]' [-Wformat=]
  scanf("%s %s",&a,&b);
             ^
/in/foo.c:9:2: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  while(ch=getchar()&&ch!=EOF)
  ^~~~~